The present invention generally relates to a storage system, and in particular can be suitably applied to a storage system that performs power saving control.
Pursuant to the diffusion of computers, the amount of data that is being handled is increasing year by year. A storage apparatus is an apparatus that safely and efficiently retains massive data, is connected to a computer via a communication line, and provides a volume (container of data). For companies that handle vast amounts of data, a storage apparatus is an infrastructure that is essential for business continuation, and volumes and data being destroyed and becoming unavailable due to unexpected accidents or disasters, or computer viruses or application errors could have a grave impact on business.
Thus, a replication control function provided by the storage apparatus is normally used for creating a replication or backup of data. As the replication control function, there is a type that synchronizes data from a primary volume (P-VOL) to a secondary volume (S-VOL) in volume units, and a type that stores only the updated differential information of the primary volume as journal data in a journal volume (JNL VOL). Although the latter requires a small volume capacity, since the primary volume cannot be restored if it becomes unavailable, it is unfit for failure recovery. A pair configured from a primary volume and a secondary volume is referred to as a replication pair, and the replication pair has a Pair status of constantly synchronizing the data and a Suspend status that does not synchronize the data. Moreover, it is possible to use the replication control function and change the status of the replication pair from a Pair status to a Suspend status (Split), or the reverse thereof (Resync).
In addition, data centers that generally consume vast amounts of electricity are facing a significant problem of power consumption pursuant to the recent enlargement and high densification of data centers. Storage apparatuses play a big part in this problem, and technology for reducing the power consumption of storage apparatuses is attracting attention. MAID (Massive Arrays of Inactive Disks) is technology for suppressing power consumption by controlling or stopping the rotation of the magnetic disk in a hard disk, and this is being applied primarily to corporate storage apparatuses.
Japanese Patent Laid-Open Publication No. 2000-293314 describes power saving technology of changing a magnetic disk, which is not accessed from a host system such as a host for a given period of time, to a power saving mode, or turning off the power, and the MAID technology can be used for the power control of magnetic disks. As a unit for controlling power consumption, in addition to magnetic disks, there are various units in the relationship with the power supply such as an array group, a physical disk provision unit, and a rack blade, but this unit is generally referred to as a power control unit in this specification. As a result of using this kind of power saving technology, the power consumption of physical disks stored in the storage apparatus can be reduced. In reality, since data is stored in RAID Group units, a RAID Group will become the smallest unit as the basic power control unit.